Threaded component for seizure-resistant tubular threaded joint

ABSTRACT

The invention concerns a threaded component for a seizure-resistant tubular threaded joint wherein a lubricating substance is deposited in a thin film on at least the surface of the threads of the threading, said surface being treated to adsorb said lubricating substance. The lubricating substance consists of a homogeneous mixture of a) a thickening agent; b) a set of extreme-pressure additives physically and chemically compatible with the thickening agent and comprising at least an extreme-pressure additive with chemical action called chemical EP additive and capable of being used at Hertz pressures not less than 1000 Mpa&#39;s; c) an oil. The proportions of the constituents of the lubricating substance are selected such that said lubricating substance has a consistency capable of ensuring a self-induced and film-forming lubricating process. The invention also concerns a method for producing the thin film.

[0001] The present invention relates to male or female elements disposedat the end of pipes and intended to be connected by making up toconstitute galling-resistant threaded tubular connections and moreparticularly those intended for making up without the manual addition ofgrease.

[0002] Such threaded elements and threaded tubular connections are knownto be used in particular to constitute casing strings or productionstrings or drillpipe strings for hydrocarbon wells or the like, such asfor instance geothermal wells.

[0003] Such types of pipes are generally made up vertically, the freeend of the string at the surface comprising a female threaded elementwith an internal female threading.

[0004] In order to lower the string into the well, a new pipe isprovided above the string provided with a male threaded elementcomprising an external male threading corresponding to the femalethreading at the corresponding free end of the string, the malethreading of the new pipe is engaged in the corresponding femalethreading of the string and the new pipe is made up until the makeuptorque reaches a given value or a given reference. The string can thenbe lowered by the length of the pipe that has been connected and theprocess is repeated.

[0005] Because of the length of the pipes, about 10 m, it is not easy toengage the new pipe perfectly co-axially with the top of the string.Thus, the threadings suffer enormously during connection and moreparticularly, the stabbing flanks of the male and female threads whichrest against each other during engagement and are in sliding contact fora large proportion of makeup. The stabbing flanks of the threads arethus highly sensitive to the phenomenon of galling that can occur, ifnot during the first makeup at least during the subsequent makeupprocedures, a threaded tubular connection having to be capable of beingmade up and broken out many times without galling.

[0006] Galling can also occur at “metal-metal” sealing surfaces presenton the threaded elements of the threaded tubular connections known as“premium” connections, such sealing surfaces being in sliding contactunder increasing contact pressure up to the final makeup position.

[0007] This is also the case for the abutment surfaces, which come intocontact at the end of makeup.

[0008] Therefore it is out of the question to constitute purelymetal-metal sliding contact surfaces both for the threadings and for thesealing surfaces or the abutments if the threaded connection is providedtherewith, since the constitution of such surfaces would inevitablycause galling, which is unacceptable.

[0009] The conventional solution, which has been employed for manyyears, is to interpose a grease between the metallic surfaces that arein sliding contact, that grease being applied to the threaded element inbatches.

[0010] The most widely used grease is API type 5A2 or 5A3 greasespecified by the American Petroleum Institute (API) which is aheterogeneous mixture of a grease, graphite particles and Pb, Zn and Cumetals which has both anti-galling properties and fills the clearancebetween the male and female threads.

[0011] Such a grease, however, suffers from a number of disadvantages.

[0012] The first disadvantage of API grease linked to its nature is itsamount in lead, an element that is particularly noxious to health and tothe environment.

[0013] Such a grease also has other disadvantages, some of which arecommon to all greases.

[0014] Because of those characteristics, the grease is generally appliedwith a brush to the contact surfaces of the threaded elements. Care istaken that a minimum quantity of grease, measured by a minimum volume orminimum mass, is applied to the surfaces: thus Vallourec Mannesmann Oil& Gas France, in its booklet “VAM® Running Book”, produced by thecompany in July 1996 for its clients, specifies a volume of at least 25cm³ or a mass of at least 42 g of API Bul 5A2 grease to coat the contactsurfaces of male and female elements of VAM® TOP threaded connectionswith a 7″ (177.8 mm) external diameter.

[0015] This results in a certain variability in the quantities of greaseapplied to the threaded elements:

[0016] a) According to the operators in charge of the grease coatingoperation, in particular on site;

[0017] b) for the same operator, from one threaded element to another;and

[0018] c) for the same threaded element, from one point on the threadedelement to another.

[0019] The makeup operation distributes the grease in the clearancesbetween the male threads and corresponding female threads, theseclearances varying in a random manner from one threaded connection toanother due to the manufacturing tolerances for the threaded elements,and leads to ejection of surplus grease from the threaded connection.

[0020] For certain types of threaded connections, the difficulty inevacuating surplus grease may result in the production of very highpressures on the threads during makeup that may alter the measurement ofthe makeup torque, or even deform the threads and the sealing surfaces,even with tapered threadings (recommended by the API and thus widelyused) and lead in the event of excessive application to the threadingsjumping out, with a catastrophic drop of the string to the bottom of thewell.

[0021] In addition, surplus grease ejected during makeup accumulates atthe bottom of the well in large amounts taking into account the numberof threaded connections used, and block the pores of the reservoir rock,which pores must be traversed by the hydrocarbons before being recoveredby the production pipes. Such a blocking considerably affects theexploitation costs of hydrocarbon wells.

[0022] Further still, certain greases, including API 5A2 or 5A3, do notoffer sufficient anticorrosion protection because of their compositionand the conditions and duration of transport and/or storage of the pipesbefore use.

[0023] It may then be necessary at the manufacturing factory to apply agrease that is specific for transport and storage to the contactsurfaces of the threaded elements, then to eliminate it on site justbefore connecting the pipes and then to apply a final API 5A2 typegrease for makeup.

[0024] A number of other types of grease, with or without lead, havebeen described in patents concerning threaded connections.

[0025] Such greases are often heterogeneous, being charged with metallicparticles, mineral particles or thermoplastic particles to fill theclearances between the male and female threads (GB 1 086 720, U.S. Pat.No. 3,526,593) and/or to prevent galling during makeup (U.S. Pat. Nos.2,065,247, 5,275,845) or on breakout (GB 1 033 735, U.S. Pat. No.2,419,144).

[0026] The anti-galling properties of certain of the greases describedin those patents may result from the presence of extreme pressureadditives in those greases, which act chemically: U.S. Pat. Nos.2,065,247, 3,095,375.

[0027] However, those patents concern greases which as a result possessthe disadvantages of all of the greases indicated above for API 5A2 or5A3 greases.

[0028] Coatings with a solid consistency applied by the pipemanufacturer to the threads and bearing surfaces were then developed,enabling “dry” makeup of threaded connections without the need forsubsequent application of lubricant on site.

[0029] Such coatings may be metallic in nature, such as those describedin European patent EP 632 225, which employ an external layer of lead,or based on metallic oxides such as those described in EP 500 482, whichemploy an external layer of lead oxide, however those coatings involvethe undesirable presence of lead or lead compounds.

[0030] Such coatings can also be a paint or a sliding varnish.

[0031] Patent application EP 786 616 describes a method for producingsuch a sliding varnish on a threaded element, which method comprisesprior deposit of a thin layer (0.005 to 0.030 mm) of phosphate then a0.010 to 0.045 mm thick layer of a mixture of an epoxy type syntheticresin or of another type and molybdenum disulfide or tungsten disulfideand polymerizing the resin by heating.

[0032] U.S. Pat. No. 4,414,247 also describes a similar method forproducing a sliding varnish on a threaded element.

[0033] Such sliding varnishes have excellent anti-galling properties aslong as they are present. However as solid varnishes, they wear and arenot regenerated during repeated makeup-breakout operations. Thus, afterseveral makeup-breakout operations galling is observed on threadedconnections provided with such coatings, said galling being then suddenand catastrophic.

[0034] Further, if such a sliding varnish becomes locally deterioratedduring pipe transport or storage, the varnish layer cannot be repairedlocally.

[0035] The present invention seeks to obtain a male or female threadedelement for a threaded tubular connection that is particularly resistantto galling, comprising a male or female threading depending on the typeof threaded element which, being provided with a lubricating layer onthe surfaces intended to become contact surfaces, is free of thedisadvantages cited above.

[0036] In particular, the invention seeks to provide a threaded elementthat can be made up or broken out 10 times with a threaded element ofthe mating type without causing galling under severe hydrocarbon wellexploitation conditions with Hertz pressures that can be employed thatmay be more than 300 MPa between the sliding contact surfaces, withsliding velocities of 0.1 μm/s and with slide lengths of up to onemeter.

[0037] The invention also seeks to avoid catastrophic galling leadingsuddenly to an unacceptable degradation in the contact surfaces andnecessitating discarding or re-machining the threaded elements.

[0038] Still further, the invention seeks to provide a threaded elementthat does not liberate any substances that are dangerous to theenvironment such as lead or heavy metals for example.

[0039] Yet still further, the invention seeks to provide a threadedelement that can be used with the same success both in arctic regionsand in tropical or equatorial regions and after periods at the bottom ofwells, where the temperatures can reach or even exceed 160° C.

[0040] Still further, the invention seeks to provide a threaded elementthat can normally be used on the drill site or production site withoutapplying lubricant at that time, the necessary lubricant having alreadybeen applied at the factory producing the threaded element.

[0041] Yet still further, the invention seeks to ensure that theportions of the threaded element intended to come into sliding contactduring makeup and coated with lubricant at the factory cannot becorroded during transport and storage.

[0042] Yet still further, the invention seeks to ensure that thelubricant deposit produced at the factory can if necessary be repairedon site.

[0043] Of course, the invention seeks to ensure that the properties areobtained at a relatively low cost.

[0044] Further, the invention seeks to ensure that the threaded elementcan be used with success both with a mating threaded element inaccordance with the invention and with a compatible commerciallyavailable mating threaded element.

[0045] Still further, the invention seeks to ensure that the sameanti-galling properties is obtained with threaded elements comprisingone or more “metal-metal” sealing surfaces and/or at least one makeupabutment in addition to a threading.

[0046] Yet still further, the invention seeks to ensure that the sameanti-galling properties can be obtained with threaded elements forintegral threaded tubular connections or for threaded and coupledconnections, comprising all types of threadings (tapered, straight,single stage or with a plurality of stages, etc) with all types ofthread shapes (triangular, trapezoidal, etc.) with a constant or varyingthread width (wedge threads).

[0047] The invention provides a male or female threaded elementcomprising a male or female threading respectively, a lubricatingsubstance being deposited in a thin layer at least on the surface of thethreads of the threading, this surface being treated to adsorb or absorbsaid lubricating substance.

[0048] The term “thin layer of lubricating substance” means a layer witha thickness of less than 0.10 mm.

[0049] The lubricating substance used is a homogeneous mixture of:

[0050] a) a thickening agent;

[0051] b) at least one extreme pressure (EP) additive including at leastone extreme pressure additive with a chemical action, termed a chemicalEP additive; and

[0052] c) an oil.

[0053] The term “homogeneous mixture” means, as is known, an intimateand stable dispersion of the constituents, such that the lubricatingsubstance has identical properties at all points.

[0054] The proportions of the three components of the lubricatingsubstance are selected so that said lubricating substance has aconsistency able to ensure a self-fed lubrication regime and afilm-forming nature.

[0055] The notion of a “self-fed lubrication regime” is known per se tocharacterize the fact that, in lubricating substances of the oil typeand of certain greases, the layer of lubricating substance is neverirreversibly destroyed but “self-heals” or “self-joins” as it is shearedoff during makeup.

[0056] Such a characteristic can be achieved with a range of consistencyfor the lubricating substance at ambient temperature that is relativelywide, ranging from a semi-solid consistency similar to that of a highlyviscous varnish prior to drying to a pasty consistency that does notflow and resembles a wax.

[0057] It is necessary to combine the three components of thelubricating substance, thickening agent, EP additive and oil, to solvethe present problem. However, the lubricating substance can alsocomprise other substances, which are inert as regards the gallingresistance, but are added for other reasons (to color the layer, forexample).

[0058] The thickening agent, as its name implies, makes the lubricatingsubstance thick, viscous, consistent, pasty but fluid to provide theself-fed lubricating regime and the film-forming properties. It can alsoact as a binder for the other constituents of the lubricating substance.

[0059] Two chemical families of thickening agent, organic and mineral,can be distinguished:

[0060] a) organic thickening agents:

[0061] non limiting examples of organic thickening agents that can becited are animal or vegetable petroleum waxes, petrolatum waxes,oxidized petrolatum waxes, sulphonated waxes, synthetic waxes andmixtures of these waxes, tackifying petroleum resins, bitumens, polymersthat are soluble or dispersible in oil, liposoluble soaps, etc. Inaddition to the properties cited above, this type of thickening agentcan advantageously have a protective function as regards corrosionbecause of its chemical and physical characteristics.

[0062] b) mineral thickening agents:

[0063] the mineral thickening agent can be hydrophobic calcined silica,hydrophobic grafted bentonites or titanium dioxide.

[0064] Extreme pressure (EP) additives are substances that are wellknown in the lubricant field. Their performances can be measured by EPtest standards (4 ball test, Falex test, etc.).

[0065] By definition, chemical EP additives react with metallic parts incontact from a certain temperature generated by friction, creating achemical lubricating film. Among chemical EP additives the followingones are known:

[0066] chemical EP additives based on sulfur or containing sulfur, suchas for example hydrocarbons or sulfur-containing esters sold as a“sulfur-containing product”, metallic dithiocarbamates, neutral oroverbased metallic sulphonates;

[0067] chemical EP additives based on phosphorus, such as phosphoricacids or esters;

[0068] chemical EP additives based on sulfur and phosphorus, such asmetallic dithiophosphates, in particular of zinc;

[0069] chemical EP additives based on chlorine, in particularchlorinated paraffins;

[0070] modified or non-modified fatty acids or esters, complex esters,etc.

[0071] These chemical EP additives are generally produced and solddiluted in a mineral oil, but the term “chemical EP additives” as usedin the remainder of the present document will refer to the undilutedactive ingredient.

[0072] The chemical EP additive or additives used are selected fromknown additives to allow operation without galling at a Hertz pressureof 1000 MPa or more.

[0073] They are also selected so as to be physically and chemicallycompatible with the selected thickening agent: they must, therefore, beperfectly miscible with the thickening agent but must not react with itas their extreme pressure properties would be severely diminished.

[0074] These chemical EP additives can be used alone or as a mixture tobenefit from maximum synergy in performance.

[0075] The term “oil” as used in the lubricating substance means both anoil that is specifically added and an oil in which the thickening agentsand/or EP additives, in particular chemical EP additives, are dilutedwhen supplied.

[0076] The oil used can be a cut from distilling petroleum productsknown as “inorganic base”, but it can also be a synthetic base obtainedby chemical reaction such as polyalphaolefins, polyisobutenes, esters,etc. it can also be a vegetable based oil (rapeseed oil, sunflower oil,etc.) or an animal oil. It can also be a mixture of such bases.

[0077] Preferably, the chemical EP additive or additives and thickeningagent are soluble in the oil, which enables to disperse the chemical EPadditive or additives with the thickening agent and obtain a perfectlyhomogeneous lubricating substance.

[0078] Preferably, the thickening agent has chemical molecules with amarked polar nature. Such a feature can in particular make the lubricantadhere to a substrate.

[0079] Preferably, the thickening agent is chemically stable up to atemperature of 120° C. or more, preferably 160° C. or more.

[0080] Optionally, the EP additive or additives also comprise at leastone EP additive with a physical action, preferably in the form of solidsubmicronic particles to produce the lubricating substance in the formof a homogeneous mixture.

[0081] EP additives with a physical action, known as physical EPadditives, intercalate themselves between the contact surfaces in theform of a film that can shear along the characteristic cleavage planesof their crystalline structure and parallel to the plane of movement, orsimply in readily deformable planes. The first category (cleavage)includes graphite, molybdenum, tungsten or tin disulfides, boronnitride, etc., and the second category includes PTFE, polyamide,polyurea type polymers, etc.

[0082] Preferably, at least one of the components from the assembly ofEP additives has anticorrosion properties.

[0083] The total content of EP additives is preferably in the range 5%to 75% %, depending on the type of EP additive used.

[0084] In a first preferred implementation, the total content of EPadditives is in the range 5% to 50% and highly preferably in the range15% to 32% by weight.

[0085] Advantageously in this first implementation, the lubricatingsubstance comprises a plurality of chemical EP additives, preferably nonchlorinated additives.

[0086] In a first variation of the first implementation, the content ofthickening agent in the lubricating substance is in the range 5% to 60%by weight and preferably in the range 8% to 40% by weight; this resultsin an oil content in the lubricating substance which is in the range 30%to 75% and preferably in the range 40% to 60% by weight.

[0087] In a second variation of the first implementation, enabling tohave a more solid deposit consistency, the content of thickening agentin the lubricating substance is in the range 60% to 80% by weight; thisresults in an oil content in the lubricating substance in the range 5%to 20% by weight.

[0088] In a second preferred implementation in which the chemical EPadditive or additives comprise a chlorinated paraffin, the content ofthickening agent in the lubricating substance is in the range 25% to 60%by weight, and the total EP additive content in the lubricatingsubstance is in the range 40% to 75%; this results in an oil content inthe lubricating substance in the range 0.5% to 15% by weight.

[0089] The contents of thickening agent and EP additives given for thedifferent compositions of the present document correspond to thecontents of active substances of the indicated constituents.

[0090] Preferably, the weight of the layer of lubricating substance onthe threaded element is in the range 0.1 g/m² to 40 g/m².

[0091] In a variation, the surface of the threads, treated to adsorb orabsorb the lubricating substance, is the surface of a layer selectedfrom the group formed by phosphatation layers, oxalation layers andmetal layers.

[0092] In a variation, the surface of the threads is treated to endow itwith a controlled roughness so as to adsorb or absorb the lubricatingsubstance. Such a treatment can, for example, be sanding, shot blasting,etching or the like.

[0093] Preferably, the surface of the threading threads is treated toadsorb or absorb the lubricating substance over a depth in the range0.003 mm to 0.080 mm.

[0094] Advantageously, the lubricating substance is also deposited oneach sealing surface when the threaded element under considerationcomprises such sealing surfaces.

[0095] Advantageously again, the lubricating substance is also depositedon each abutment surface when the threaded element under considerationcomprises such abutments.

[0096] Advantageously again, all the surfaces on which the lubricatingsubstance is intentionally deposited as a thin layer are surfaces thatare treated to adsorb or absorb the lubricating substance.

[0097] The present invention also aims to protect a galling-resistantthreaded tubular connection that comprises a male threaded element and afemale threaded element, each provided with a corresponding threading,the threadings being made up one into the other during connection, inwhich at least one of the two threaded elements is a threaded element ofthe invention as described above.

[0098] In a variation of this threaded connection, only one of the twothreaded elements is a threaded element of the invention as describedabove, the other threaded element comprising a thin layer of thelubricating substance defined above deposited directly on at least thesurface of the threads.

[0099] The lubricating substance is a homogeneous mixture of:

[0100] a) a thickening agent;

[0101] b) at least one extreme pressure additive, the extreme pressureadditive or additives being physically and chemically compatible withthe thickening agent and comprising at least one extreme pressureadditive with a chemical action, termed a chemical EP additive, that canbe used at Hertz pressures of 1000 MPa or more; and

[0102] c) an oil.

[0103] The term “directly deposited thin layer of lubricating substance”means that the surface of the threads under consideration has not beentreated to adsorb or absorb the lubricating substance.

[0104] The present invention also aims to protect a method for producinga thin layer of a lubricating substance on a male or female threadedelement for a galling-resistant threaded tubular connection as describedabove, the threaded element comprising a male or female threadingrespectively.

[0105] The method of the invention comprises the following steps:

[0106] a) preparing a homogeneous liquid mixture comprising:

[0107] a volatile solvent;

[0108] a thickening agent;

[0109] at least one extreme pressure additive, the extreme pressureadditive or additives being physically or chemically compatible with thethickening agent and comprising at least one extreme pressure additivewith a chemical action that can be used at Hertz pressures of 1000 MPaor more; and

[0110] an oil;

[0111] b) applying a thin layer of substantially uniform thickness ofsaid liquid mixture at least to the surface of the threads of thethreaded element; and

[0112] c) evaporating off the solvent naturally or forcedly.

[0113] The term “volatile solvent” means any petroleum cut withdistillation temperatures in the range 40° C. to 250° C. These volatilesolvents include special gasolines, white spirits, burning oils,aromatic products such as benzene, toluene, xylene, etc.

[0114] Optionally, at least the surface of the threads of the threadedelement is treated to adsorb or absorb the lubricating substance to beapplied.

[0115] Preferably, the viscosity of the liquid mixture, measured by FORDn°4 cup, corresponds to a duration in the range 10 s to 30 s, preferablyin the range 15 s to 25 s.

[0116] Preferably again, the layer of liquid mixture is applied byspraying.

[0117] As an alternative, it can be applied by any other means:immersion, painting, sprinkling.

[0118] The solvent can be evaporated off naturally or in a forcedmanner, in particular by moderate heating of the threaded element or byhot air convection.

[0119] The following figures provide non-limiting illustrations of anumber of implementations of the invention.

[0120]FIG. 1 shows a type of threaded and coupled connection comprising4 threaded tubular elements that may be used by the invention.

[0121]FIG. 2 shows a further type of threaded and coupled connectioncomprising 4 threaded tubular elements that may be used by theinvention.

[0122]FIG. 3 shows an integral type threaded type connection comprising2 threaded tubular connections that may be used by the invention.

[0123]FIG. 4 shows a few male threads of a male threaded tubular elementof the commerce shown in FIG. 1.

[0124]FIG. 5 shows a few female threads of a female threaded tubularelement of the invention of the type shown in FIG. 1.

[0125]FIG. 6 shows a detail of FIG. 5.

[0126]FIG. 7 shows the stabbing phase at the beginning of make up of themale and female threads of FIGS. 4 and 5.

[0127]FIG. 8 shows the same male and female elements of FIGS. 4 and 5once make up is completed.

[0128]FIG. 9 shows a few male threads of a male threaded tubular elementfor a threaded tubular connection of the invention of the type shown inFIG. 2.

[0129]FIG. 10 shows a few female threads of a female threaded tubularconnection of the type shown in FIG. 2.

[0130]FIG. 11 shows the stabbing phase at the beginning of make up ofthe male and female threads of FIGS. 9 and 10.

[0131]FIG. 12 shows a detail of FIG. 11.

[0132]FIG. 13 shows the same male and female elements of FIGS. 9 and 10once make up is completed.

[0133]FIG. 14 shows a variation of FIG. 9.

[0134]FIG. 15 shows the male and female threads of FIGS. 14 and 10 oncemake up is completed.

[0135]FIG. 16 shows the free end zone of the male element shown in FIG.2.

[0136]FIG. 17 shows a housing zone inside a female threaded tubularelement of the invention shown in FIG. 2.

[0137]FIG. 18 shows the free end zone of FIG. 16 and the housing zone ofFIG. 17 after make up of the threaded elements.

[0138]FIG. 19 is a graph representing the makeup curve for a threadedconnection of FIGS. 9 to 13 and 16 to 18.

[0139]FIG. 20 is a graph representing, for a threaded connection ofFIGS. 9 to 13 and 16 to 18, the relative evolution of the shoulderingtorque during make up and that of the initial breakout torque as afunction of the number of makeup-breakout cycles.

[0140]FIG. 1 shows a threaded connection 100 in accordance with APIspecification 5CT between two metal pipes 101 and 101′ using a coupling102 and comprising 2 threaded connections.

[0141] Each end of pipe 101, 101′ comprises a male element 1,1′comprising a male tapered threading 103, 103′ with “round” threads andterminates in a male end surface 109, 109′.

[0142] Coupling 102 comprises 2 female elements 2, 2′ symmetricallydisposed with respect to the median plane of the coupling, each femaleelement comprising a female tapered threading 104, 104′ with threadsthat mate with the male threads.

[0143] Male threadings 103, 103′ are made up into mating femalethreadings 104, 104′.

[0144] API specification 5B defines the thread shape, dimension,threading taper, pitch, etc for this type of connection.

[0145] Although not shown, a connection with “buttress” type threadingscan also be used under API specification 5CT and 5B disposed in the sameway as that of FIG. 1, but with trapezoidal threads.

[0146]FIG. 2 shows a threaded and coupled connection 200 with two maleelements 1,1′ and two female elements 2,2′ with tapered threadings 203,204 and with trapezoidal threads, coupling 202 having a lug 206 in itscentral portion between the female elements, the lug enabling to makethe fluid flow in a non turbulent way in pipes 201, 201′, and to providefemale abutments 210 which bear against the male abutments 209constituted by the annular end surfaces of the pipes.

[0147] Tapered male and female sealing surfaces 207 and 208, disposed onthe non threaded portions and radially interfering so as to produce anelastic contact pressure between them enable to provide a seal for theconnection of FIG. 2 in known manner.

[0148]FIG. 3 shows an integral threaded connection 300 between two pipes301 and 302 comprising two-stage straight threadings.

[0149] The end of pipe 301 comprises a male element 1 comprising astraight two-stage male threading 303, 303′, a tapered male shouldersurface 307 in a half dovetail between the two male thread stages andabutments 309, 309′ at each end of the male element.

[0150] The end of pipe 302 comprises a female element 2 that mates withthe male element 1 and comprises a straight two-stage female threading304, 304′, a tapered female shoulder surface 308 in a half dovetailbetween the two female thread stages, and abutments 310, 310′ at eachend of the female element.

[0151] The male and female threadings of coupling 300 have trapezoidalthreads and normally have no radial interference after makeup.

[0152] In the connected state, shoulders 307, 308 form the principalabutment, abutments 309, 309′, 310, 310′ only acting as a backupabutment in case of sinking of the principal abutment.

[0153] Tapered surfaces 311′, 312′ on the male and female elementsrespectively form an internal pair of metal-metal sealing surfaces, inthe vicinity of the end of the male element. In the vicinity of the endof the female element, the tapered surfaces 311, 312 form, an externalpair of metal-metal sealing surfaces. The external pair of sealingsurfaces 311, 312 could also be placed between shoulders 307, 308 andthe large diameter threading stage 303, 304.

[0154]FIG. 4 shows a longitudinal section of a few triangular threads 11of the male tapered threading 103 of FIG. 1.

[0155] Male threads 11 comprise two rectilinear flanks 13, 15 eachmaking an angle of 30° with respect to the normal YY to axis XX of thethreaded element and either side of that normal, a male rounded threadcrest 17 and a male thread root 19, also rounded.

[0156] Flank 15, the normal to the surface of which is directed towardsthe free male end 109, is the flank known as the stabbing flank becausethe male stabbing flank rests on the female stabbing flank duringengagement of the male and female threads for connection by makeup.

[0157] Flank 13, the normal to the surface of which is directed towardsthe side opposite the male free end 109, is the load flank. The loadflanks support the axial tensile load on the threaded connections.Surfaces 13, 15 and zones 17, 19 of the male threads are as machined.

[0158]FIG. 5 shows a longitudinal section through a few triangularthreads 12 of the female tapered threading 104 of FIG. 1.

[0159] The form of female threads 12 corresponds to the form of malethreads 11, each with a stabbing flank 16 and a load flank 14, placed at30° either side of the normal YY to the axis of the threaded element, afemale thread crest 20 and a female thread root 18.

[0160] Surfaces 14, 16 and zones 18, 20 of the female threads aretreated to absorb or adsorb a lubricating substance and to this end,comprise a layer 32 for conversion by manganese phosphatation with athickness of 0.006 mm produced on the surfaces of the as machinedthread. The manganese phosphatation layer is well suited to treatingunalloyed or light alloy steel threaded elements.

[0161] Other phosphatation layers are also possible, such as a zincphosphatation layer, for example.

[0162] In the case of steel threaded elements with a high chromiumcontent or a nickel based alloy, it may be advisable to produce thelayer by oxalation or by means of a deposit of copper metal.

[0163] The thickness desired for the different layers is of the sameorder of magnitude as that for the manganese phosphatation.

[0164] The treated surface of the female threads 12 is coated with athin layer 22 of a lubricating substance that is partially adsorbed orabsorbed into the phosphatation layer and which covers the latter by athickness of a few microns in a substantially uniform manner over thetreated surface of threads 12. The ratio between the weight of theadsorbed or absorbed layer in the phosphatation layer and the weight ofthe layer over the phosphatation layer is about 1/1.

[0165] The following compositions are examples of compositions (weight%) and of weight of layer (g/m²) of suitable lubricating substance.

EXAMPLE 1

[0166] petroleum paraffin wax: 19% sulfur-containing product:  6%overbased sulphonates: 13% metallic dithiophosphate:  3% mineral oil:59% Weight of deposit: 20 g/m²

[0167] The lubricating substance comprises three chemical EP additives,namely the sulphur-containing product, the overbased sulphonates and themetallic dithiophosphate, which are oil-soluble constituents. The wax isalso soluble in the oil.

EXAMPLE 2

[0168] oxidized petrolatum wax:  29% sulfur-containing product:  6%overbased calcium sulphonates:  13% metallic dithiophosphate (Zn):  3%mineral oil:  49% Weight of deposit:  20 g/m² Kinematic viscosity ofdeposit at ±100° C. 260 cSt

[0169] It should be noted that oxidized petrolatum waxes are verytemperature-stable compounds that are not deteriorated chemically whenthe temperature is maintained at 160° C. Such a chemical stabilityenables the threaded connections to be lowered to the bottom of wellswhere the temperature can reach 160° C. without irreversible changes inthe characteristics of the wax; the threaded connections can then beraised from the well for breakout before being made up again and droppedagain into the same well or into another well.

EXAMPLE 3

[0170] petrolatum wax: 31% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 47% Weightof deposit: 24 g/m²

EXAMPLE 4

[0171] tackifying petroleum resin: 30% sulfur-containing product:  6%overbased sulphonates: 13% metallic dithiophosphate:  3% mineral oil:48% Weight of deposit: 21 g/m²

EXAMPLE 5

[0172] sulphonated wax: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 21 g/m²

EXAMPLE 6

[0173] bitumen: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 22 g/m²

EXAMPLE 7

[0174] aluminium stearate: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 23 g/m²

EXAMPLE 8

[0175] lipophilic bentonite:  9% sulfur-containing product:  7%overbased sulphonates: 13% metallic dithiophosphate:  3% mineral oil:68% Weight of deposit: 14 g/m²

EXAMPLE 9

[0176] polyalkylmethacrylate (organic thickening agent): 12%sulfur-containing product:  6% overbased sulphonates: 12% metallicdithiophosphate:  4% mineral oil: 66% Weight of deposit: 23 g/m²

EXAMPLE 10

[0177] oxidized petrolatum wax: 39% polyisobutene  2% chlorinatedparaffin: 59% Weight of deposit: 21 g/m²

[0178] In this Example 10, the chlorinated paraffin has an oilyconsistency; a small proportion of oil is added in the form ofpolyisobutene (synthetic base).

[0179] The use of chlorinated paraffin as a chemical EP additive rendersthis composition more particularly suitable for use with certainstainless steel threaded elements (not susceptible to corrosion bychlorine or chlorides) or nickel alloy threaded elements.

EXAMPLE 11

[0180] oxidized petrolatum wax:  67% sulfur-containing product:  5%overbased calcium sulphonates:  12% metallic dithiophosphate (Zn):  5%mineral oil:  11% Weight of deposit:  23 g/m² Kinematic viscosity ofdeposit at +100° C.: 560 cSt

[0181] In all of the above examples, the deposits of lubricatingsubstances obtained are smooth because of the film-forming nature of thelubricating substance and the liquid mixture from which it originates.

[0182] In all of the above examples except for Examples 5 and 9, thedeposits of the lubricating substance obtained have a waxy, adhesiveappearance, do not flow and thus have a pasty consistency at ambienttemperature; by way of indication, the viscosity of such deposits is inthe range 100 cSt to 1000 cSt at +100° C., the temperature that can beobtained when making up the threaded elements.

[0183] In the case of Examples 5 and 9, the appearance of the deposit ismore that of a very viscous varnish and its consistency is semi-solid.

[0184] In all of the examples apart from Example 10, the lubricatingsubstance comprises three chemical EP additives as the EP additive, thetotal content of EP additive being around 20-25%.

[0185] In Examples 1 to 9, the ratio between the sulfur-containingproduct, overbased sulphonates and metallic dithiophosphate issubstantially 2:4:1. In Example 11, it is substantially 1:2:1.

[0186] The content of oil in the lubricating substance varies widelydepending on the nature of the thickening agent and/or EP additives andthe desired consistency:

[0187] about 50% for Examples 1 to 7;

[0188] about 65-70% for Examples 8 (thickening agent=lipophilicbentonite) and 9 (more flowing consistency);

[0189] about 10% for Example 11 (relatively solid waxy consistency);

[0190] only about 2% for Example 10 because of the oily consistency ofthe proportion of paraffin selected.

[0191] In all of the examples comprising an organic thickening agent,i.e., in all of the examples except for Example 8, the thickening agentcontains chemical molecules with a marked polar nature, which allow itto adhere to the treated metallic surface of the threads and give it ahydrophobic nature. Such an adhesive hydrophobic nature allows the thinlayer 22 of lubricating substance to perfectly cover the treated surfaceof the threads and to protect this surface against corrosion, inparticular when the pipes are stored with their threaded elements priorto use.

[0192] All the compositions of these 11 examples produce a welding loadin the ASTM D2596 “4 ball” test (EP test) of more than 800 kg and a wearmark diameter of 0.35 to 0.37 mm after 1 hour at 392 N (40 kgf) of loadduring ASTM D2266 wear tests.

[0193] All of the chemical EP additives of the 11 examples arephysically and chemically compatible with the corresponding thickeningagents. The chemical EP additives must remain stable until they aresubjected to temperatures resulting from local rupture of thelubricating film and enabling those additives to then react chemicallywith the metallic surfaces in contact to form constituents preventing ordelaying galling even when the contact pressure exceeds 1000 MPa.

[0194] In addition to a thickening agent, EP additives and an oil, thelubricating substance can optionally comprise less than 5% of a coloranthaving no action as regards the anti-galling properties but intended toindicate the presence of a thin layer of the lubricating substance ofthe invention (traceability and differentiation over standard APIgreases).

[0195] Thus the lubricating substance can comprise 2.5% of powderedcarbon black to endow the lubricating substance with a highlyhomogeneous black color, or 0.12% of fluorescein (Fluorescent GreenLight) to endow the lubricating substance with a dark green color.

[0196]FIG. 7 shows female threads 12 during the stabbing phase duringtheir connection to male threads 11 by makeup.

[0197] The layer of lubricating substance 22 prevents direct contact ofthe as machined male stabbing flanks 15 and female stabbing flanks 16treated by phosphatation.

[0198] Because makeup has only just started and because of the tapereddisposition of the threadings, there remains a free space between thelayer 22 and the surface of the male thread at the load flanks 13, 14and the thread crests and roots.

[0199] Layer 22 supports the weight of pipe 101 at the stabbing flanks,pipe 101 being made up in the vertical position above coupling 102already connected to pipe 101′ and the high torque provided by themakeup tongs.

[0200] Even a slight misalignment of the axes of the male and femalethreaded elements 1,2 during engagement would, in the absence of anylubricating layer, result in ploughing of the stabbing flank surfacesand very rapid galling of the contacting flanks: it then would beimpossible to break out the galled threaded connections and in anyevent, the deteriorated surfaces of the thread would have to bereconditioned.

[0201] The presence of a thickening agent and of oil in the lubricatingsubstance of layer 22 and the viscosity of the lubricating substanceensure that in the presence of shear stresses, there is a self-fedlubrication regime that is typical of an oil or grease. This results inthe absence of cracking of the lubricating substance on shear forexternal operating temperatures in the range −50° C. to +50° C.; it canalso be said that the lubricating substance self-heals or self-joins asit is being sheared.

[0202] The phosphatation layer 32 on the surface of the female threads12 can efficiently retain the lubricating substance on the surface ofthese threads.

[0203] Under extreme pressure conditions when self-feeding of thelubricating substance is interrupted locally, the chemical extremepressure additive takes up the baton for preventing galling.

[0204]FIG. 8 shows the male and female threads 11, 12 in the final madeup position.

[0205] The lubricating substance of the thin layer 22 is distributed inthe clearances between the helical surfaces of the threads duringmakeup. It comes between load flanks 13, 14 and between stabbing flanks15, 16 and it more or less fills the clearances between thread crestsand roots 17, 18, 19, 20 following the pairing due to dimensionaltolerances.

[0206] For this reason, excess lubricating substance is not ejected intothe well and the threaded elements cannot be deformed by the pressuresexerted by a great excess of lubricating substance.

[0207] Breakout of the connected threads leads to separation of layer 22into 2 parts, which separation is random in nature within that layer.

[0208] Nevertheless the remainders of the layers on the male and femalethreads can allow at least 10 makeup-breakout cycles to be carried outwithout the onset of galling.

[0209] On the other hand the inventors have noted that simply adding aconventional API 5A2 type grease reduced with respect to the standardquantities required in a manner to simply fill the clearances betweenthe threads rapidly leads to galling after a few makeup/breakout cyclesif addition is not renewed between cycles.

[0210]FIG. 9 shows a longitudinal section of a few male trapezoidalthreads 51 of the male tapered threading 203 of FIG. 2.

[0211] Male threads 51 comprise four rectilinear faces, namely:

[0212] a load flank 53;

[0213] a stabbing flank 55;

[0214] a thread crest 57;

[0215] a thread root 59.

[0216] The thread crests and roots are parallel to the pitch taper ofthreading 103.

[0217] In a variation, not shown, they could be parallel to the axis ofthe connection, the radial height of the stabbing flank then beinggreater than that of the load flank.

[0218] Load flank 53 makes a slightly negative angle A with the normalto the axis of the threaded element, for example −3°, such that there isa slight overhang.

[0219] Stabbing flank 55 makes a positive angle B with the normal to theconnection axis such that threads 51 are narrower at their base than atthe crest 57, which facilitates machining.

[0220] The 4 faces 53, 55, 57, 59 of threads 51 are coated in the asmachined state with a deposit 21 that is a few micrometers thick of thesame lubricating substance as that formed by deposit 22 in FIG. 5. Thesame compositions and the same weights of layer can be applied as thosedescribed for FIG. 5.

[0221]FIG. 10 shows a longitudinal cross section of a few femaletrapezoidal threads 52 of the female tapered threading 204 of FIG. 2.

[0222] Female threads 52 comprise four rectilinear faces with a shapeand disposition that correspond to those of the male threads 51, namely:

[0223] a load flank 54 with a slightly negative angle A;

[0224] a stabbing flank 56 with a positive angle B;

[0225] a thread crest 60;

[0226] a thread root 58.

[0227] Faces 54, 56, 58, 60 are treated by manganese phosphatation inorder to produce a 0.006 mm thick phosphatation layer 32, as is the casewith FIG. 5.

[0228] The thus treated surface of the female threads 52 is coated witha thin layer 22 of the same lubricating substance as that described forFIG. 5.

[0229] This lubricating substance is absorbed or adsorbed on the treatedsurface of threads 52 and covers this surface to a thickness of a fewmicrometers in a uniform manner. The same compositions and the sameweights of layers can be applied as those described in respect of FIG.5.

[0230] As for FIG. 5, manganese phosphatation can be replaced by anothersurface treatment that is more suitable to the metal of the threadedelement in order to produce surfaces that are suitable for adsorbing orabsorbing the lubricating substance.

[0231]FIG. 11 shows female threads 52 during the stabbing phase whenbeing connected to male threads 51 by makeup.

[0232] At the stabbing flanks 55, 56 (see FIG. 12), layers 21, 22 formjust one layer 23 whereas they are distinct between the other faces thatare not in contact during the stabbing phase.

[0233] Layer 23 supports the weight of pipe 201 to be connected, themakeup torque and possibly any side forces if the axis of the maleelement makes an angle with the axis of the female element.

[0234] When makeup is complete (FIG. 13), the lubricating substancesubstantially fills all the clearances between threads 51, 52 andprevents direct contact between the load flanks 53, 54 under tension andbetween the female thread crest 60 and the male thread root 59 whichradially interfere.

[0235]FIG. 14 shows a variation of FIG. 9 in which layer 21 oflubricating substance is not directly produced on the as machinedsurface of the male threads but on an initially deposited phosphatationlayer 31 similar in nature and thickness to that 32 on the surface ofthe female threads 52 of FIG. 10.

[0236] Such a configuration enables to better hold back the lubricatingsubstance on the surface of the male threads and to obtain a connectionshown in FIG. 14 with the corresponding female threads of FIG. 10, whichconnection is particularly suitable for undergoing many makeup-breakoutcycles without the risk of galling.

[0237] Such a threaded connection of FIG. 15, on the other hand,requires phosphatation both on the coupling 202 and on pipes 101, 101′and thus is more expensive than the connection of FIG. 13.

[0238]FIG. 16 shows the free end zone of pipe 201 and thus of the malethreaded element of FIG. 2.

[0239] In FIG. 16, layer 21 of the lubricating substance covers not onlythe surface of male threads 51 of FIG. 9 but also the whole of theexternal peripheral surface of the male element beyond the threading,and more particularly at 27 the male sealing surface 207 and at 29 themale abutment surface 209 at the end of the pipe. The weight of thelayer deposited on surfaces 207, 209 is substantially similar as thatdeposited on the surface of the male threads.

[0240]FIG. 17 shows the female housing zone for the male end of coupling202 of FIG. 2.

[0241] In FIG. 17, the internal surface of the female element betweenthreading 204 and lug 206 is treated in the same manner as the surfaceof female threads 52 of FIG. 10 by manganese phosphatation (layer 32)and is coated with a layer 22 of lubricating substance, like the surfaceof those threads 52.

[0242] More particularly, layers 32 and 22 coat the female bearingsurface 208 at 38 and 28 and the female abutment 210 at 40 and 30.

[0243] These layers can readily extend over the internal peripheralsurface of the lug 206 and over the external peripheral surface of thecoupling 202.

[0244] The thickness of the phosphatation layer is substantiallyidentical for the sealing surface 208, the female abutment 210 and thefemale threads 52.

[0245] Similarly, the weight of the layer of lubricating substance issubstantially identical for the sealing surface 208, the female abutment210 and the female threads 52.

[0246]FIG. 18 shows the connection in the made up position of the malefree end of FIG. 16 with the corresponding female zone of FIG. 17.

[0247] During makeup, the layers of lubricating substances 27, 28 comeinto contact with each other.

[0248] As make up continues, these layers held back by the phosphatationlayer 38 prevent direct contact of the metal surfaces of the sealingsurfaces and prevent them from galling in particular when surfaces 207,208 are only slightly inclined and when contact of these surfaces up tothe final made up position is produced over a considerable length.

[0249] The mechanism for the action of the lubricating substance is thesame as that at the thread surfaces.

[0250] At the very end of makeup, layers 29, 30 at the level of theabutment surfaces 209, 210 come into contact and prevent these surfacesfrom galling by the same mechanism.

[0251] The phosphatation layer 40 also acts to hold back as much of thefilm of lubricating substance as possible. Although not shown, one couldalso think of depositing the lubricating layer at 27 and 29 (malesealing surface and abutment) not directly on the as machined metalsurface but on surfaces treated by phosphatation, as is the case in FIG.17.

[0252] It is also easy to apply the teaching of FIGS. 4 to 18 tostraight threadings with one or more stages such as those at 303, 303′,304, 304′ of the integral threaded connection of FIG. 3 as well as tothe abutment and sealing surfaces existing on said connection.

[0253] Other implementations that have not been described are alsoencompassed by the present invention, in particular when thephosphatation layer is produced at the surface of the thread of the malethreaded element and not the female threaded element (oppositeconfiguration to that shown for FIGS. 1-18).

[0254] The invention is applicable to any male or female threadedelement regardless of the disposition of the threading or the threadedportions, to any thread form, to any thread width, which may be constantor may vary along the threading, to interfering or non-interferingthreads, with or without contact or interference over the two flanks ofthe same thread, whether the threaded connection obtained is of athreaded and coupled type or integral type. It is also applicableregardless of the number, form and disposition of the bearing surfaceand abutment.

[0255] We shall now describe non-limiting examples of a method fordepositing the lubricating substance in a thin layer on the surface ofthreads, sealing surfaces and/or abutments to obtain thegalling-resistant connections described above.

[0256] A liquid mixture is prepared with a viscosity that is measuredusing a FORD n° 4 cup at 25° C.; some non-limiting examples of theformulation are given below. The numbers for these examples of theliquid mixture formulation respectively correspond to those used in theabove examples of the composition of the lubricating substance, the “dryextract” of the lubricating substance corresponding to the liquidmixture of the same example.

EXAMPLE 1

[0257] special hydrocarbon solvent: 20% mineral oil: 47% petroleumparaffin wax: 15% sulfur-containing product:  5% overbased sulphonates:10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 20 s

EXAMPLE 2

[0258] special hydrocarbon solvent (white spirit): 23% mineral oil: 37%oxidized petrolatum wax: 22% sulfur-containing product:  5% overbasedsulphonates: 10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:20 s

EXAMPLE 3

[0259] special hydrocarbon solvent: 20% mineral oil: 37% petrolatum wax:25% sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 21 s

EXAMPLE 4

[0260] special hydrocarbon solvent: 22% mineral oil: 37% tackifyingpetroleum resin: 23% sulfur-containing product:  5% overbasedsulphonates: 10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:18 s

EXAMPLE 5

[0261] special hydrocarbon solvent: 22% mineral oil: 37% sulphonatedwax: 23% sulfur-containing product:  5% overbased sulphonates: 10%metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 16 s

EXAMPLE 6

[0262] special hydrocarbon solvent: 22% mineral oil: 37% bitumen: 23%sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 17 s

EXAMPLE 7

[0263] special hydrocarbon solvent: 20% mineral oil: 39% aluminiumstearate: 23% sulfur-containing product:  5% overbased sulphonates: 10%metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 18 s

EXAMPLE 8

[0264] special hydrocarbon solvent: 20% mineral oil: 54% lipophilicbentonite:  8% sulfur-containing product:  5% overbased sulphonates: 10%metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 17 s

EXAMPLE 9

[0265] special hydrocarbon solvent: 20% mineral oil: 52% 50%polyalkylmethacrylate: 10% sulfur-containing product:  5% overbasedsulphonates: 10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:22 s

EXAMPLE 10

[0266] special hydrocarbon solvent: 42% oxidized petrolatum wax: 23%polyisobutene:  1% chlorinated paraffin: 34% FORD n ° 4 cup viscosity:20 s

EXAMPLE 11

[0267] special hydrocarbon solvent (heptane): 40% mineral oil:  7%oxidised petrolatum wax: 40% sulfur-containing product:  3% overbasedsulphonates:  7% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:20 s

[0268] All these liquid mixtures are intimate and stable; thus, they arehomogeneous and after eliminating the solvent, produce a homogeneouslubricating substance as defined above.

[0269] These liquid mixtures can readily be prepared in advance andstored in closed vessels prior to use. If necessary, the mixture cansimply be homogenized prior to use.

[0270] The mixture has to be applied in a thin layer to the male andfemale threaded elements of FIG. 2 with a substantially uniformthickness and more particularly for each of the threaded elements ontheir threading 203, 204, on the sealing surface 207, 208 and on theabutment 209, 210.

[0271] The fact that the organic thickening agents used for the mixturesof Examples 1 to 7 and 9 to 11 contain chemical molecules with a markedpolar nature allows the liquid mixture to adhere better to the substrateto be coated.

[0272] The content of solvent in the liquid mixtures is of the order of20% for Examples 1 to 9 and of the order of 40% for Examples 10 and 11.It varies as a function of the consistency of the dry extract obtainedafter evaporation of the solvent and the nature of the solvent (whitespirit, heptane, etc.).

[0273] The male threaded elements 1 that are at the end of pipes 201 areplaced in the as machined state under a spray head of the type used tophosphate the male threaded elements.

[0274] The spray head is supplied at low pressure (1 to 3 bars relative)with the liquid mixture and sprays the liquid mixture over the externalsurface of the threaded elements.

[0275] Because of the low viscosity of the liquid mixture, itdistributes itself in a film of uniform thickness over the entireperiphery of the threading 203, the sealing surface 207 and the abutment209.

[0276] The thickness of the liquid mixture film is a function of theviscosity of the mixture which is itself a function of the content ofoil and volatile solvent: a large content of oil and volatile solventreduces the viscosity of the mixture and thus the thickness of theliquid film.

[0277] The solvent is then evaporated off completely to obtain a layerof lubricating substance with a substantially uniform thickness.

[0278] The drying time for the liquid mixture is linked to theevaporation time for the solvent, which is a function of the nature ofthe solvent (shorter time for heptane than for white spirit, forexample) and of the drying temperature.

[0279] Female threaded elements 2 to be coated are located insidecouplings 202.

[0280] Couplings 202 have already undergone, in known manner, amanganese phosphatation treatment which has coated the threading 204,the sealing surface 208 and the abutment 210 of each of the two femalethreaded elements with a fine phosphate conversion layer about 0.006 mmthick.

[0281] Couplings 202 are then individually placed in paint tanks, whichcontain spray nozzles supplied with the liquid mixture and directed soas to project fine droplets of liquid mixture onto the threading, thesealing surface and the abutment of each female threaded element.

[0282] The thickness of the resulting film of liquid mixture is afunction of the viscosity of the liquid mixture, the spray pressure, thespray nozzle diameter and the spray duration.

[0283] The couplings are then withdrawn from the paint tank and dried bycirculating hot air until the solvent has been completely evaporatedoff.

[0284] Each coupling 202 is then made up in the factory in a standardmanner using one of its two female threaded elements onto a malethreaded element of one of the two ends of pipe 101.

[0285] In a known manner, the second female threaded element of thecoupling 202 that is not made up and the second male threaded elementthat is not made up at the other end of pipe 201 are then protected byprotectors in order to prevent pollution of these threaded elements byabrasive particles during transport or storage, which can deterioratethe sealing performance during use in a petroleum well.

[0286] The applied lubricating substance has hydrophobic andanti-corrosive properties that can protect the threaded elements fromcorrosion during storage and transport.

[0287] If, however, the lubricating substance became polluted, it couldbe easy to eliminate the layer as if it were a grease, by high waterpressure or by petroleum solvent, to apply a new film of liquid mixture,for example using a brush, and to evaporate off the solvent.

[0288] Adding colorant to the lubricating substance can facilitatechecking these operations of eliminating the layer of pollutedlubricating substance and its reconstitution.

[0289] Alternatively, standard API type grease can be applied to thethreaded element, coated or uncoated or partially uncoated oflubricating substance. The lubricating substance is completelycompatible with API type grease.

[0290] Such repair procedures are not possible with sliding varnishes.

[0291] We now show, in FIG. 19, two makeup curves obtained with VAM TOP®threaded connections from the VAM® catalogue, n° 940 edited by theApplicant, with dimensions of 5½″×17 lb/ft (external pipe diameter 139.7mm and pipe thickness 7.72 mm), of light alloy steel, heat treated,grade L80 (elastic limit of 551 MPa or more).

[0292]FIG. 19 shows the makeup torque T up the ordinate as a function ofthe number of turns N for two tests A and B, curves A and B having beenoffset along the X axis for easier reading.

[0293] Curve A relates to a connection of the invention: the malethreaded element is similar to that of FIG. 9 (as machined trapezoidalthreads coated with the lubricating substance with the composition ofExample 2) and the female threaded element is similar to that of FIG. 10(trapezoidal threads phosphated with manganese and coated with the samelubricating substance with the composition of Example 2).

[0294] Curve B relates to a reference connection lubricated in astandard manner with API 5A2 grease.

[0295] In curves A and B, once engagement has occurred between the maleand female threaded element, the makeup torque rises steadily because ofsliding of the corresponding faces of the threads under contactpressure. The makeup torque increases significantly as the radialinterference between the male and female threads resulting from thedimensional characteristics of the threaded connections is high.

[0296] Note at a given time the increase in the slope of the makeupcurve which shows the appearance of radial interference between thesealing surfaces 207-208. Curves A and B in FIG. 19 are characteristicof threaded connections with high interference between the sealingsurfaces.

[0297] From point S, the makeup torque increases almost vertically andshows the coming into contact of abutments 209/210.

[0298] Point F indicates the final makeup torque, which is locatedbetween the minimum makeup torque (T_(min)) and the maximum makeuptorque (T_(max)) specified for this type of threaded connection.

[0299] Curve A obtained for a threaded connection of the invention isvery similar to that of B obtained for a threaded connection lubricatedby an API grease both from its appearance and from the shoulderingtorque T_(S) and the final torque T_(F). This shows that the coefficientof friction of the lubricating substance of the present invention issimilar to that of the standard API grease.

[0300] For the two curves A and B, the shouldering torque Ts is equal toabout 70% of the optimum makeup torque specified for this type ofthreaded connection because of the particular pairing of the threadedelements tested (high interferences both between the threadings andbetween the sealing surfaces).

[0301] Curves A and B in FIG. 20 show, for VAM TOP® threaded connectionssimilar to those of the preceding figure and treated in the same manner,the variation in the shouldering torque as a function of the number ofcycles of makeup-breakout carried out (up to 10 cycles), the shoulderingtorque being expressed by a relative value with respect to the optimummakeup torque, this latter being an average value between the minimummakeup torque and the maximum torque specified.

[0302]FIG. 20 shows that the shouldering torque varies little duringthese 10 makeup-breakout cycles and that the stability of theshouldering torque is better for a threaded connection of the invention(curve A) than for a connection coated with API grease (curve B) evenwhen the coating is renewed between makeup-breakout cycles: theshouldering torque T_(S) varies from 69% of the optimum makeup torque onthe 1^(st) makeup to 58% on the 10^(th) makeup in the case of curve Acompared to 70% on the 1st makeup and 36% on the 6th makeup in the caseof curve B. This shows that sufficient lubricating substance remains ona threaded connection of the invention to obtain stable lubricatingcharacteristics both in the threads and in the bearing surfaces after 10makeup-breakout cycles.

[0303] Curves C and D in FIG. 20 show for respectively the same threadedconnections as those for curves A and B of FIG. 20, the variation in theinitial breakout torque as a function of the number of breakouts for 10consecutive makeup-breakout cycles, this variation being expressed withrespect to the final makeup torque.

[0304] The first teaching provided by curve C in FIG. 20 (threadedconnection of the invention) is that, because of the absence of galling,the connection can always be broken out.

[0305] The initial breakout torque varies for curve C between 97% and106% of the final makeup torque, again showing stable performances.

[0306] In the case of curve D of FIG. 20 (API grease), the initialbreakout torque varies between 84% and 101% of the final makeup torque,giving a slightly greater variation than with curve C.

[0307] The final visual appearance of the threads and sealing surfacesafter 10 makeup-breakout cycles is excellent, with no trace of galling.

[0308] The table below compares the number of makeup-breakout cyclesobtained before the appearance of galling for a maximum of 10 cyclescarried out on the same type of VAM TOP® 5 ½″ 17 lb/ft grade L80threaded connections as for the tests of FIGS. 19 and 20, but thethreaded elements are selected to have low interference between thethreadings and high interference between the bearing surfaces. Number ofcycles before galling threaded connection with API 5A2 grease ≧10(reference) threaded connection with dry MoS₂ varnish 6 threadedconnection of present invention with ≧10 lubricating substance accordingto Example 2

[0309] The results confirm that the application of a prior art MoS₂ dryvarnish rapidly leads to unacceptable galling, while that of thelubricating substance defined above produces satisfactory resultscomparable, from the point of view of galling, with the results obtainedwith connections coated with API grease.

1. A male or female threaded element (2) for a threaded tubularconnection that is resistant to galling, comprising a respective male orfemale threading (104, 204), a lubricating substance being deposited asa thin layer (22) on at least the surface (14, 16, 18, 20, 54, 56, 58,60) of the threads (12, 52) of the threading, said surface being treatedto adsorb or absorb said lubricating substance, characterized in thatthe lubricating substance is a homogeneous mixture of: a) a thickeningagent; b) at least one extreme pressure additive, the extreme pressureadditive or additives being physically and chemically compatible withthe thickening agent and comprising at least one extreme pressureadditive with a chemical action termed a chemical EP additive which iscapable of use at Hertz pressures of 1000 MPa or more; and c) an oil;the proportions of the constituents of the lubricating substance beingselected so that said lubricating substance has a consistency thatensures a self-fed lubrication regime and a film-forming nature.
 2. Athreaded element according to claim 1, characterized in that thechemical EP additive or additives and the thickening agent are solublein the oil.
 3. A threaded element according to claim 1 or claim 2,characterized in that the thickening agent contains chemical moleculesof a marked polar nature.
 4. A threaded element according to any one ofclaims 1 to 3, characterized in that the thickening agent is chemicallystable up a temperature of 120° C. or more, preferably 160° C. or more.5. A threaded element according to any one of claims 1 to 4,characterized in that the thickening agent is an organic thickeningagent.
 6. A threaded element according to any one of claims 1 to 4,characterized in that the thickening agent is a mineral thickeningagent.
 7. A threaded element according to any one of claims 1 to 6,characterized in that the chemical EP additive or additives are selectedfrom the group formed by sulfur-based or sulfur-containing chemical EPadditives, those based on phosphorus, those based on sulfur andphosphorus, those based on chlorine and those based on modified or nonmodified esters or modified or non modified fatty acids or those basedon complex esters.
 8. A threaded element according to any one of claims1 to 7, characterized in that the organic thickening agent is anoxidized petrolatum wax, in that a plurality of chemical EP additives isused, comprising a sulfur-containing product, an overbased sulphonateand a metallic dithiophosphate, and in that the oil is a mineral oil. 9.A threaded element according to any one of claims 1 to 8, characterizedin that the EP additive or additives comprise at least one EP additivewith a physical action in the form of solid sub-micronic particles. 10.A threaded element according to any one of claims 1 to 9, characterizedin that at least one of the EP additive or additives has anti-corrosionproperties.
 11. A threaded element according to any one of claims 1 to10, characterized in that the total content of EP additives in thelubricating substance is in the range 5% to 50% by weight and preferablyin the range 15% to 32% by weight, and in that the EP additives includea plurality of chemical EP additives.
 12. A threaded element accordingto claim 11, characterized in that the content of thickening agent inthe lubricating substance is in the range 5% to 60% by weight andpreferably in the range 8% to 40% by weight, and in that the content ofoil in the lubricating substance is in the range 30% to 75% by weight.13. A threaded element according to claim 11, characterized in that thecontent of thickening agent in the lubricating substance is in the range60% to 80% by weight, and in that the content of oil in the lubricatingsubstance is in the range 5% to 20% by weight.
 14. A threaded elementaccording to any one of claims 1 to 10, characterized in that thechemical EP additive or additives comprise a chlorinated paraffin, thecontent of thickening agent in the lubricating substance is in the range25% to 60% by weight, in that the total content of EP additives in thelubricating substance is in the range 40% to 75% by weight, and in thatthe content of oil in the lubricating substance is in the range 0.5% to15% by weight.
 15. A threaded element according to any one of claims 1to 14, characterized in that the weight of the layer of lubricatingsubstance is in the range 0.1 g/m² to 40 g/m².
 16. A threaded elementaccording to any one of claims 1 to 15, characterized in that thesurface (14, 16, 18, 20, 54, 56, 58, 60) of the threads, treated toadsorb or absorb the lubricating substance, is the surface of a layer(32) selected from the group formed by phosphatation layers, oxalationlayers and metallic layers.
 17. A threaded element according to any oneof claims 1 to 16, characterized in that the surface (14, 16, 18, 20,54, 56, 58, 60) of the threads is treated to endow said surface with acontrolled roughness so as to adsorb or absorb the lubricatingsubstance.
 18. A threaded element according claim 16 or claim 17,characterized in that the surface (14, 16, 18, 20, 54, 58, 56, 60) ofthe threads is treated to adsorb or absorb the lubricating substanceover a depth in the range 0.003 mm to 0.080 mm.
 19. A threaded elementaccording to any one of claims 1 to 18, characterized in that, thethreaded element comprising at least one sealing surface (208), thelubricating substance is also deposited in a thin layer (28) on eachsealing surface.
 20. A threaded element according to any one of claims 1to 19, characterized in that, the threaded element comprising at leastone makeup abutment (210), the lubricating substance is also depositedin a thin layer (30) on each surface of the abutment.
 21. A threadedelement according to claim 19 or claim 20, characterized in that all ofthe surfaces on which the lubricating substance is deposited as a thinlayer are surfaces that are treated to adsorb or absorb the lubricatingsubstance.
 22. A threaded element according to any one of claims 1 to21, characterized in that the lubricating substance comprises less than5% by weight of a colorant that is inactive as regards thegalling-resistant properties.
 23. A galling-resistant threaded tubularconnection comprising a male threaded element and a female threadedelement, each of said threaded elements comprising a correspondingthreading, said threadings being made up one into the other to aconnected position, characterized in that at least one of the twothreaded elements is a threaded element according to any one of claims 1to
 22. 24. A threaded tubular connection according to claim 23,characterized in that only one of the two threaded elements is athreaded element (2) according to any one of claims 1 to 22, the otherthreaded element (1) being provided at least on the surface of thethreads (51) of its threading (203) with a lubricating substancedirectly deposited as a thin layer (21), the lubricating substance beinga homogeneous mixture of: a) a thickening agent; b) at least one extremepressure additive, the extreme pressure additive or additives beingphysically and chemically compatible with the thickening agent andcomprising at least one extreme pressure additive with a chemical actiontermed a chemical EP additive which is capable of use at Hertz pressuresof 1000 MPa or more; and c) an oil; the proportions of the constituentsof the lubricating substance being selected so that said lubricatingsubstance has a pasty consistency with a viscosity in the range 40 to400 cSt at a temperature of +40° C., a film-forming nature and beingcapable of ensuring a self-fed lubrication regime.
 25. A method forproducing a thin layer of a lubricating substance on a male or femalethreaded element for a galling-resistant threaded tubular connection,the threaded element comprising a respectively male or female threading,the lubricating substance having an adhesive pasty consistency, afilm-forming nature and being capable of ensuring a self-fed lubricatingregime, in which: a) a homogeneous liquid mixture is prepared, formedby: a volatile solvent; a thickening agent; at least one extremepressure additive, the extreme pressure additive or additives beingphysically and chemically compatible with the thickening agent andcomprising at least one extreme pressure additive with a chemical actionthat is capable of use at Hertz pressures of 1000 MPa or more; and anoil; b) a thin layer of said liquid mixture of substantially uniformthickness is applied to at least the surface of the threads of thethreading, said surface of the threads of the threading optionallyhaving been treated to absorb or adsorb said lubricating substance; andc) the volatile solvent is evaporated off or allowed to evaporate off.